ARS | Publication request: Molecular variation among and within improved cultivars in the U.S. cotton germplasm collection

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 15, 2011
Publication Date: January 1, 2012
Citation: Hinze, L.L., Dever, J.K., Percy, R.G. 2012. Molecular variation among and within improved cultivars in the U.S. cotton germplasm collection. Crop Science. 52:222-230.

Interpretive Summary: Agricultural productivity is dependent on genetically diverse resources that can be transferred into improvement programs. There is a need to assess the diversity of the vast amount of resources available in the U.S. Cotton Germplasm Collection. Resources that are available for cotton improvement in the U.S. Cotton Germplasm Collection often are under-utilized because they are not sufficiently characterized to encourage breeders' interest in using these accessions. To make these resources more available, a group of accessions was chosen that represents the most readily accessible genetic variation in this collection. This group of improved cultivars was chosen from accessions collected from different countries and time periods in the history of cotton breeding. Analysis of phenotypic and molecular data demonstrate that both inter- and intra-cultivar genetic diversity is present among these cultivars, but larger patterns of diversity based upon region or era of development are generally poor or lacking. This information will provide cotton breeders with more accurate guidance in the selection of unique and desirable parental germplasm from the U.S. Cotton Germplasm Collection to improve cultivated cotton grown in the United States.

Technical Abstract: Many cotton (Gossypium spp.) accessions conserved in the U.S. Cotton Germplasm Collection are not sufficiently characterized to encourage breeders' interest in using these accessions. This study was conducted to determine the genetic variability of several groups of improved cultivar accessions and how this variability can be used to enhance current breeding programs. These groups were selected based on region or era of development and included cultivars from China, northern and southern Africa, along with obsolete and recent U.S. cultivars. Both inter- and intra-cultivar diversity was observed among these cultivars, but larger patterns of diversity based upon region or era of development were generally poor or lacking. Heterozygosity levels averaged 44% for all groups, with Chinese cultivars showing the lowest polymorphism (72%) and PIC values (0.332). The African cultivars showed the highest levels of intra-cultivar molecular variation with 13.4% polymorphic loci. The majority of molecular diversity was found within groups (62.2%) and within cultivars (31.0%) rather than among groups (6.8%). Using canonical discriminant analysis, we identified isolated clusters based on cultivars with similar phenotypes. This information will provide cotton breeders with more accurate guidance in the selection of unique and desirable accessions to introduce diversity, reduce vulnerability, and provide improvements for yield, agronomic, and fiber quality traits.